Many modern electrical or electronic devices contain a visual display. For example, mobile telephones, porkable and particularly palm-held digital computers each contain a (typically) backlit liquid crystal display (LCD) screen. In each case, the desire to miniaturise and thus increase the portability of such devices is balanced by the need to ensure that the screen that imparts information to the user has an adequate viewing area. In the field of mobile telephones, the emergence of technologies to view Internet pages has provided a further need to increase screen size.
Although a screen can be provided which is physically larger than the device to which it belongs, such a screen is susceptible to damage and increases the overall size of the device. Furthermore, there are practical difficulties in forming larger screens of height and width 45 cm or greater, for example.
Another problem with devices employing electrical screens in particular is that the active display area (that is, the area over which text and images is displayed, usually via an array of pixels) is by necessity smaller than the overall area of the screen. Typically, the screen has a glass cover plate and will also have an edge, which may or may not form a part of the cover plate. The edge must be of finite width, in order to protect the screen and mechanically support the glass cover plate. In LCDs, an edge is in any event necessary to contain the liquid crystals. Usually, the transistors and other electronic components necessary to drive the LCD are located adjacent the active display area as well. This means that the edge of the display is visible to a viewer of the screen.
A number of approaches have been taken to try and address the problem of the visible edge or edges of screens and LCD screens in particular. JP-A-090185046 (Casio Computer Co., Ltd.) shows a display device having two display elements with refraction plates overlaying them. A diffusion plate overlays the refraction prate. The refraction plate bends light rays from across the display elements so as apparently to close the gap between two adjacent plates so as to form a large display from two smaller ones. The problem with this arrangement is that the display device becomes heavier and more complex through the inclusion of the refraction plates.
EP-A-0,179,913 (Matsushita Electric Industrial Co., Ltd.) shows an alternative approach. Here, a light guide is employed to guide the rays from the LCD elements to he viewing surface. Since a light guide is employed for each pixel, this arrangement would be expensive to manufacture.
Finally, EP-A-0,559,070 shows an LCD panel where an attempt has been made to reduce the gap itself. The LCD panels are bent by 90° at the edges so as to bring the active area physically closer to the edge. Then, the edge seal and contacts extend downwards from the surface of the screen and do not contribute to the gap. Even then, the gap is only reduced (to perhaps 1-2 mm), and whilst this would potentially be adequate for large wall displays using adjoining screens, it would still be visible in smaller (e.g. hand holdable) screens. Moreover, the manufacture of the screens of EP-A-0,559,070 would be much more difficult than with ‘standard’ LCDs.